Heretofore the energetic plasticizer DNDA-6-7, a ternary mixture of N,Nxe2x80x2-dimethylbis-nitramine (DNDA-5; approx. 43%), N-methyl-Nxe2x80x2-ethyl-bisnitramine (DNDA-6; approx. 45%) and N,Nxe2x80x2-diethylbisnitramine (DNDA-7; approx. 12%), has been made in the following manner:
1. Nitration of N,Nxe2x80x2-dimethylurea
1.1. Batch reaction with an acid mixture (mixture of nitric acid and sulfuric acid) with the addition of urea dissolved in dichloromethane at about xe2x88x9210xc2x0 C.
1.2. Stopping the reaction by pouring it onto ice water.
1.3. Collecting the reaction mixture (main product: dinitridimethylurea) in dichloromethane by shaking it out.
1.4. Neutralizing the dichloromethane with sodium hydrogen carbonate.
2. Hydrolysis of the dinitrodimethylurea.
2.1. Mixing the dichloromethane phase with water, evaporating the dichloromethane, followed by hydrolysis at about 100xc2x0 C.
2.2. Collecting the methylnitramine in dichloromethane
3. Nitration of N,Nxe2x80x2-diethylurea.
3.1. Batch reaction with a mixture of acids (mixture of nitric acid and sulfuric acid) with the addition of the urea dissolved in dichloromethane at about xe2x88x9215xc2x0 C.
3.2. Stopping the reaction by pouring it onto ice water.
3.3. Collecting the reaction mixture (main product dinitrodiethylurea) in dichlormethane by shaking.
3.4. Neutralizing the dichloromethane phase with sodium hydrogen carbonate.
4. Hydrolysis of the dinitrodiethylurea.
4.1. Mixing the dichloromethane phase with water, evaporating the dichloromethane, followed by hydrolysis at about 100xc2x0 C.
4.2. Collecting the ethylnitramine in dichloromethane.
5. Condensation
5.1. Condensing the methyl and ethyl nitramine in common in a fixed ratio of about 2:1 at max. 0xc2x0 C. with 70% sulfuric acid and p-formaldehyde in dichloromethane.
5.2. Stopping the reaction by pouring onto ice water.
5.3. Collecting the reaction mixture (ternary mixture of the nitramines) in dichloromethane by shaking.
5.4. Neutralizing the dichoromethane phase with sodium hydrogen carbonate.
The method outlined above is not capable of producing large amounts of the plasticizer in an economically practical manner.
It was therefore the problem of the invention to provide a method for producing a DNDA type plasticizer, especially a method for the production of DNDA-6-7.
This problem was solved by a method in which the following changes were made in the method known in the state of the art:
Instead of the acid mixture, highly concentrated nitric acid is used in a definite excess, preferably about an 11-fold molar excess. This change makes it possible to recycle the nitric acid; also, surprisingly few byproducts are formed.
The ureas are not dissolved in dichloromethane, but are used in solid form. The advantages of this variant: less volume of liquid, no dilution effect.
N,Nxe2x80x2 dimethylurea and N,Nxe2x80x2-diethylurea are not nitrated separately but together at max. 5xc2x0 C. in the desired molar ratio, preferably a molar ratio of about 2:1 (DNDA-5-7). The advantage is that process steps can be eliminated.
The reaction mixture (main products: dinitrodimethylurea and dinitrodiethylurea) is collected in dichloromethane by counter-current extraction. This saves process steps and the separation efficiency is optimized.
Combined hydrolyzation of the mixture thus obtained, at about 100xc2x0 C., in the given molar ratio. Advantage: saving of process steps.
The entire reaction is performed continuously. Thus it is possible to remove the reaction heat more easily, the reaction volumes are reduced, thereby reducing potential dangers.
With the changes according to the invention, of the method known in the state of the art, it is possible to produce DNDA directly in a high yield, with a high purity, and in the desired composition.
By means of an HPLC study it was surprisingly found that both the desired products and the desired compositions are produced and that additional byproducts are not formed by this kind of conduct of the process of the invention.
It is expressly pointed out that it is not necessary to perform all of the steps of the process in the manner according to the invention. An improvement of the method described in the state of the art is achieved when at least one of them is performed. An especially preferred practice of the method, however, is the combining of all of the variants of the invention.